From a single cell far too small to be seen with the naked |eye|, the embryo grows in length in the first 6 weeks of interuterine life to about 2/10" or 5 mm. During the embryonic period the main parts of the neck and face develop, as do the genital organs, bones, ~nerves~, muscles, and some sense organs. The |spinal cord|, |brain|, |ears| and |eyes| have started their development. The tissue from which the |lungs| form appears as well as the earliest parts of the |stomach|, |liver|, |pancreas|, intestines and |kidneys|. There are two pairs of limb buds, from which the arms and legs will take shape. The primitive |heart| has started to beat.